How to use a different database for each branch in Rails

Nate Berkopec asked on Twitter:

With a Rails app, how do you manage switching between a bunch of different branches that have different DB schemas/migration states? Blowing away the whole DB every time gets old fast.

I agree, it does get old fast, but luckily Ruby and Rails has the building blocks necessary to help us out.


Put this in your config/database.yml:

  database: my_application_<%= `git branch --show-current`.strip %>


Our goal here is to have a database for each branch so we can be sure that our database changes don’t persist when we switch branches. For this to work we need…

  1. The name of the current branch.
  2. A way to tell Rails (well, ActiveRecord) what database name to use.
  3. A database for each branch.

How to get the name of each branch

If you are using git version 2.22 or later, you’ve got git branch --show-current to return the name of the current branch:

$ git branch --show-current

If you’re on an older version of git you should be able to get there using a bit of command-line-fu:

$ git branch | grep "*" | cut -d " " -f 2

I haven’t verified this, though.

How to tell ActiveRecord what database name to use

We usually configure the database connections in config/database.yml. That file is parsed as YAML, but it also supports ERB. This is already used in the default generated database.yml, which contains

  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>

All we need to do is configure our database name in the same manner, so something like:

  database: <%= insert_my_database_name_here %>

We already know how to get the current branch name from git, so we can shell out and run the git command for that:

  database: your_app_name_<%= `git branch --show-current`.strip %>

With the above in place in config/database.yml, ActiveRecord will see your database name as your_app_name_main when the current branch is main and your_app_name_break_things if the branch is break_things - and that’s what we want.

How to have a database for each branch

Unfortunately the magic stops here. You still have to create (and drop) the databases you need, and run migrations and seeds and whatnot.

Thankfully, with Rails’ Actionable Errors this has become less cumbersome.


If you like using weird characters in your branch names, like having branches called bug/1234-fix or whatever, your DBMS needs to support those characters in database names. As it turns out, PostgreSQL is perfectly fine having a database named your_app_name_bug-1234-fix - I haven’t verified on other systems.

If this is a problem for you, you might be able to do something like this to remove unwanted characters:

  database: your_app_name_<%= `git branch --show-current`.gsub(/\W/, "") %>

Further ideas

If you are using PostgreSQL, you might be able to configure schema_search_path in roughly the same manner to have just the one development database. I have not investigated this, though 🤔